Driver warning in electric power steering systems

ABSTRACT

Technical solutions are described for providing driver warning using steering systems. An example steering system includes a motor control system that sends a command to a motor. The steering system further includes a fault monitoring system that sets a fault indication flag by monitoring one or more components of the steering system. The steering system further includes a driver warning feedback system that generates a warning injection signal based on and in response to the fault indication flag being set. Further, the motor control system generates a driver feedback by modifying the command to the motor using the warning injection signal, and sending the modified command to the motor.

CROSS-REFERENCES TO RELATED APPLICATIONS

This patent application is a continuation-in-part of to U.S. patentapplication Ser. No. 15/785,917, filed Oct. 17, 2017, which isincorporated herein by reference in its entirety.

BACKGROUND

The present application generally relates to electric power steeringsystems (EPS), and particularly to providing driver warnings via theEPS.

Safety requirements in a contemporary EPS require advanced failuremonitoring, including both prognostics and diagnostics, for ensuringsafe operation of both the hardware and software components of the EPS.With improved diagnostics, there is an increasing need for providingwarning when the EPS is approaching a failure condition, or once thefailure has occurred. With the inclusion of fault tolerant control in amodern EPS, typical ways of alerting the driver that have beendeveloped, include reducing the assist provided by the EPS so that theEPS feels heavy to a driver and the driver is, to an extent, iscautioned to take the EPS for repair.

SUMMARY

One or more embodiments are described for providing driver warning usingsteering systems. An example steering system includes a motor controlsystem that sends a command to a motor. The steering system furtherincludes a fault monitoring system that sets a fault indication flag bymonitoring one or more components of the steering system. The steeringsystem further includes a driver warning feedback system that generatesa warning injection signal based on and in response to the faultindication flag being set. Further, the motor control system generates adriver feedback by modifying the command to the motor using the warninginjection signal, and sending the modified command to the motor.

An example method for providing driver warning feedback using a motorcontrol loop in a steering system includes generating a command to besent to a motor for generating torque. The method further includesreceiving an indication flag that is indicative of a fault in one ormore components of the steering system. The method further includesgenerating a warning injection signal based on and in response to thefault indication flag being set. The method further includes generatinga driver feedback by modifying the command with the warning injectionsignal, and sending the modified command to the motor.

Further, according to one or more embodiments, a driver warning feedbacksystem includes a fault monitoring and arbitration module that monitorsa fault indication flag that is indicative of a fault in operation ofone or more components of a steering system, and determines a type ofdriver feedback to provide in response to the fault indication flagbeing set. The driver warning feedback system further includes aninjection signal calculation module that computes a warning injectionsignal based on the type of the driver feedback to be provided, thecomputation including determining a frequency, phase, and amplitude ofthe warning injection signal. The injection signal calculation modulefurther sends the warning injection signal to a motor control system ofthe steering system for superimposing the warning injection signal on acommand sent to a motor of the steering system to generate the driverfeedback.

Further yet, according to one or more embodiments, a warning system isdescribed that includes a first motor control system that sends a firstcommand to a first motor in a first actuator. The warning system alsoincludes a second motor control system that sends a second command to asecond motor in a second actuator. Further, the warning system includesa fault monitoring system that sets a fault indication flag bymonitoring one or more components of the first and second motor controlsystems and generates a warning injection signal in response to thefault indication flag being set. The first actuator generates a firstaudible noise using the first motor by modifying the first command usingthe warning injection signal, and sending the modified first command tothe first motor. The second actuator generates a second audible noise bymodifying the second command using the warning injection signal, andsending the modified second command to the second motor.

These and other advantages and features will become more apparent fromthe following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 depicts an EPS system according to one or more embodiments;

FIG. 2 depicts a block diagram of the EPS system with an example driverwarning module according to one or more embodiments;

FIG. 3 depicts a block diagram of a portion of an example driver warningsystem according to one or more embodiments;

FIG. 4 illustrates a flowchart of an example method of providing adriver warning feedback according to one or more embodiments;

FIG. 5 is an exemplary embodiment of a steer by wire (SbW) steeringsystem according to one or more embodiments;

FIG. 6 depicts a block diagram and operational flow in a steer by wiresystem that includes a driver warning system according to one or moreembodiments;

FIG. 7 depicts a block diagram with separate fault monitoring systemsfor the handwheel actuator and the roadwheel actuator according to oneor more embodiments; and

FIG. 8 depicts a flowchart of a method for generating a driverfeedback/warning in a steer by wire system according to one or moreembodiments.

DETAILED DESCRIPTION

As used herein the terms module and sub-module refer to one or moreprocessing circuits such as an application specific integrated circuit(ASIC), an electronic circuit, a processor (shared, dedicated, or group)and memory that executes one or more software or firmware programs, acombinational logic circuit, and/or other suitable components thatprovide the described functionality. As can be appreciated, thesub-modules described below can be combined and/or further partitioned.

Referring now to the Figures, where the technical solutions will bedescribed with reference to specific embodiments, without limiting same,FIG. 1 is an exemplary embodiment of an electric power steering system(EPS) 40 suitable for implementation of the disclosed embodiments. Thesteering mechanism 36 is a rack-and-pinion type system and includes atoothed rack (not shown) within housing 50 and a pinion gear (also notshown) located under gear housing 52. As the operator input, hereinafterdenoted as a steering wheel 26 (e.g. a hand wheel and the like) isturned, the upper steering shaft 29 turns and the lower steering shaft51, connected to the upper steering shaft 29 through universal joint 34,turns the pinion gear. Rotation of the pinion gear moves the rack, whichmoves tie rods 38 (only one shown) in turn moving the steering knuckles39 (only one shown), which turn a steerable wheel(s) 44 (only oneshown).

Electric power steering assist is provided through the control apparatusgenerally designated by reference numeral 24 and includes the controller16 and an electric machine 46, which could be a permanent magnetsynchronous motor, a permanent magnet direct current motor, a switchedreluctance motor, or any other type of motor, are is hereinafter denotedas motor 46. The controller 16 is powered by the vehicle power supply 10through line 12. The controller 16 receives a vehicle speed signal 14representative of the vehicle velocity from a vehicle velocity sensor17. Steering angle is measured through position sensor 32, which may bean optical encoding type sensor, variable resistance type sensor, or anyother suitable type of position sensor, and supplies to the controller16 a position signal 20. Motor velocity may be measured with atachometer, or any other device, and transmitted to controller 16 as amotor velocity signal 21. A motor velocity denoted ω_(m) may bemeasured, calculated or a combination thereof. For example, the motorvelocity ω_(m) may be calculated as the change of the motor position θas measured by a position sensor 32 over a prescribed time interval. Forexample, motor speed ω_(m) may be determined as the derivative of themotor position θ from the equation ω_(m)=Δθ/Δt where Δt is the samplingtime and Δθ is the change in position during the sampling interval.Alternatively, motor velocity may be derived from motor position as thetime rate of change of position. It will be appreciated that there arenumerous well-known methodologies for performing the function of aderivative.

As the steering wheel 26 is turned, torque sensor 28 senses the torqueapplied to the steering wheel 26 by the vehicle operator. The torquesensor 28 may include a torsion bar (not shown) and a variableresistive-type sensor (also not shown), which outputs a variable torquesignal 18 to controller 16 in relation to the amount of twist on thetorsion bar. Although this is one type of torque sensor, any othersuitable torque-sensing device used with known signal processingtechniques will suffice. In response to the various inputs, thecontroller sends a command 22 to the electric motor 46, which suppliestorque assist to the steering system through worm 47 and worm gear 48,providing torque assist to the vehicle steering.

It should be noted that although the disclosed embodiments are describedby way of reference to motor control for electric steering applications,it will be appreciated that such references are illustrative only andthe disclosed embodiments may be applied to any motor controlapplication employing an electric motor, e.g., steering, valve control,and the like. Moreover, the references and descriptions herein may applyto many forms of parameter sensors, including, but not limited totorque, position, speed and the like. It should also be noted thatreference herein to electric machines including, but not limited to,motors, hereafter, for brevity and simplicity, reference will be made tomotors only without limitation.

In the control system 24 as depicted, the controller 16 utilizes thetorque, position, and speed, and like, to compute a command(s) todeliver the required output power. Controller 16 is disposed incommunication with the various systems and sensors of the motor controlsystem. Controller 16 receives signals from each of the system sensors,quantifies the received information, and provides an output commandsignal(s) in response thereto, in this instance, for example, to themotor 46. Controller 16 is configured to develop the necessaryvoltage(s) out of inverter (not shown), which may optionally beincorporated with controller 16 and will be referred to herein ascontroller 16, such that, when applied to the motor 46, the desiredtorque or position is generated. Because these voltages are related tothe position and speed of the motor 46 and the desired torque, theposition and/or speed of the rotor and the torque applied by an operatorare determined. A position encoder is connected to the steering shaft 51to detect the angular position θ. The encoder may sense the rotaryposition based on optical detection, magnetic field variations, or othermethodologies. Typical position sensors include potentiometers,resolvers, synchros, encoders, and the like, as well as combinationscomprising at least one of the forgoing. The position encoder outputs aposition signal 20 indicating the angular position of the steering shaft51 and thereby, that of the motor 46.

Desired torque may be determined by one or more torque sensors 28transmitting torque signals 18 indicative of an applied torque. One ormore exemplary embodiments include such a torque sensor 28 and thetorque signal(s) 18 therefrom, as may be responsive to a complianttorsion bar, T-bar, spring, or similar apparatus (not shown) configuredto provide a response indicative of the torque applied.

In one or more examples, a temperature sensor(s) 23 located at theelectric machine 46. Preferably, the temperature sensor 23 is configuredto directly measure the temperature of the sensing portion of the motor46. The temperature sensor 23 transmits a temperature signal 25 to thecontroller 16 to facilitate the processing prescribed herein andcompensation. Typical temperature sensors include thermocouples,thermistors, thermostats, and the like, as well as combinationscomprising at least one of the foregoing sensors, which whenappropriately placed provide a calibratable signal proportional to theparticular temperature.

The position signal 20, velocity signal 21, and a torque signal(s) 18among others, are applied to the controller 16. The controller 16processes all input signals to generate values corresponding to each ofthe signals resulting in a rotor position value, a motor speed value,and a torque value being available for the processing in the algorithmsas prescribed herein. Measurement signals, such as the above mentionedare also commonly linearized, compensated, and filtered as desired toenhance the characteristics or eliminate undesirable characteristics ofthe acquired signal. For example, the signals may be linearized toimprove processing speed, or to address a large dynamic range of thesignal. In addition, frequency or time based compensation and filteringmay be employed to eliminate noise or avoid undesirable spectralcharacteristics.

In order to perform the prescribed functions and desired processing, aswell as the computations therefore (e.g., the identification of motorparameters, control algorithm(s), and the like), controller 16 mayinclude, but not be limited to, a processor(s), computer(s), DSP(s),memory, storage, register(s), timing, interrupt(s), communicationinterface(s), and input/output signal interfaces, and the like, as wellas combinations comprising at least one of the foregoing. For example,controller 16 may include input signal processing and filtering toenable accurate sampling and conversion or acquisitions of such signalsfrom communications interfaces. Additional features of controller 16 andcertain processes therein are thoroughly discussed at a later pointherein.

In one or more examples, the technical solutions described hereinfacilitate the use of the electric drive portion of the EPS system, andmore specifically, the motor control loop (including the current(torque) control system and the electric motor and various sensors), toprovide warning to the driver when a failure is either about to occur(prognostics) or has already occurred (diagnostic) and the EPS 40 isstill in operation. The warning may be provided through feedback to thedriver in different ways, including tactile feedback, acoustic feedback,and the like or a combination thereof. Further, because fail-safeconditions may potentially last over periods of time (for instance, whenthe driver decided to keep operating even with reduced assist fordurations above predetermined thresholds), which may be within oneignition cycle or over multiple cycles, the technical solutionsdescribed herein facilitate implementing a time-varying warningmechanism is also described, where the amount of warning feedback isvaried over time. The warning system according to the technicalsolutions described herein may be implemented in an identical mannerirrespective of the configuration of the motor control system (i.e.,feedback or feedforward control). The technical solutions describedherein thus address the technical challenge of providing an activefeedback to a driver using an EPS to indicate a diagnostic and/or aprognostic condition with the EPS. The technical solutions describedherein thus facilitate an improvement to a typical EPS by providing suchan active feedback notification system.

FIG. 2 depicts a block diagram of the EPS according to one or moreembodiments. The controller 16 of the EPS 40 includes a steering controlmodule 210 that generates a motor torque command based on one or morecontrol signals, such as the handwheel torque and motor velocity, amongothers. The steering control may use any algorithm to determine thetorque command. In one or more examples, the controller 16 furtherincludes a power limiting module 220 that modifies the motor torquecommand based on predetermined limits, which may be configurable. In oneor more examples, the predetermined limits are computed by thecontroller 16 in real time; alternatively, the predetermined limits arepreconfigured values. The modified torque command is provided as aninput torque command to a motor control system 230.

The motor control system 230, upon receipt of the input torque commandgenerates the corresponding voltage commands to be send to the inverter260 such that the inverter 260 applies a voltage to the motor 46 togenerate the desired torque (Te). The generated torque is applied to themechanical system 36, for example, to maneuver the wheel 44. In one ormore examples, the torque generated includes the assist torque thatboosts the handwheel torque applied by the driver at the driver input26.

In addition, the controller 16 includes a failure monitoring system 240that monitors the one or more components of the EPS 40, including thehardware and software components. For example, the failure monitoringsystem 240 monitors the mechanical components, for example using one ormore sensors, and compares the one or more sensor values with estimatedvalues that are computed using an electro-mechanical model of the EPS40. If the measured values exceed the estimated values by predeterminedthresholds, the failure monitoring system 240 deems that a failurecondition has occurred (diagnostic) or is about to occur (prognostic).

In one or more examples, the failure monitoring system 240 generatesflags indicating either a failure that is about to occur, referred to asa Prognostics Flag P hereafter, or the occurrence of a failure, referredto as a Diagnostics Flag D. The flags may be binary values, such assoftware flags. Further, in one or more examples, the failure monitoringsystem 240 monitors multiple components in the EPS 40, and hence P and Dmay be matrix values indicating the status of the multiple components.The technical solutions described herein facilitate providingwarning/feedback to the driver, irrespective of which specific componentcauses failure flag(s) to be set, and/or how the failure monitoringsystem 240 detects the failure condition.

Typically, in response to one of the P and D flags from the failuremonitoring system being set, the controller 16 either causes the EPS 40to shutdown, which could include disconnecting the voltage source,turning off the gate drive (and thus the inverter) and disabling variousfunctions within the EPS 40 (such as software components), or modifyingthe system behavior of the EPS 40 by changing specific functions ortuning. For instance, when the system behavior is to be changed, say fora current sensor failure, the failure monitoring system 240 initiates atorque command modification and transitions the motor control system 230to feedforward control mode from a feedback control mode.

The technical solutions described herein, in addition to the systembehavior modification(s), facilitate signal injection(s) and commandmodification(s) to provide driver warning feedback. In one or moreexamples, the injected signal is superimposed on the base signals ascalculated by the one or more components of the controller 16. The basesignals and commands are the control signals and the commands, such asthe torque command, the current command, and the voltage command thatare generated by the one or more components of the controller 16. In oneor more examples, the base commands may be replaced by the warninginjection signals.

For example, as depicted in FIG. 2, the controller includes a driverwarning system 250 that receives the flags D and P from the failuremonitoring system 240 and generates the signal injections and/or commandmodifications.

FIG. 3 depicts a block diagram of an example driver warning systemaccording to one or more embodiments. The driver warning system 250, asdepicted, includes a failure monitoring and arbitration (FMA) module310, an injection signal calculation module 330, and a fault durationmonitoring module 340, among other components.

The FMA module 310 evaluates the type of flags set by the failuremonitoring system 240 and determines the warning signal(s) that are tobe injected for the driver. By determining the warning signal(s) the FMAmodule 310 determines the type of warning feedback generated for thedriver. The driver warning feedback may be tactile, acoustic, or acombination of both. Further, the driver warning feedback may bedetermined based on a specific signature of a fault that is detected bythe fault monitoring system 240. For example, the signature may be astate of the diagnostic and prognostic flag(s) of the fault monitoringsystem 240. Alternatively, or in addition, the fault monitoring system240 sends the signature as a separate signal to the FMA module 310, forexample, upon a request from the FMA module 310.

Based on the type of the warning feedback to be generated, the injectionsignal calculation module 330 computes the injection signal and sends itto the corresponding module/location in the controller 16. The injectionsignal calculation module 330 receives different control signals such asthe position, motor velocity, vehicle speed, and the like, which areused to determine the different warning injection signals. For example,the injection signal calculation module 330 computes pulsating injectionsignals to modify the torque command, the current command, and/or thevoltage command. The pulsating signals may be fixed frequency signals orbe functions of position and (or) velocity, for example, a sinusoidalsignal with a frequency equal to an integral multiple of the motorvelocity. As another example, the sinusoidal signal may have a frequencyequal to an integer times the position signal, i.e., a harmonic of thefundamental frequency of the motor.

For example, for the torque command signal injection, the injectionsignal calculation module 330 generates a warning-indication torquesignal (T_(wi)*) that has a fixed or varying (order based) frequency. Inone or more examples, the injection signal calculation module 330generates the warning-indication torque signal as a function of one ormore control signals in the EPS 40, such as the motor velocity, vehiclespeed, acceleration, bridge voltage etc.

Further, for the current command signal injection, the injection signalcalculation module 330 generates a warning-indication current signal(I_(wi)*) that is a direct pulsating component injected in currentcommands.

Further yet, for the voltage command signal injection, the injectionsignal calculation module 330 generates a warning-indication voltagesignal (V_(wi)*) that has a fixed or varying (order based) frequency. Inone or more examples, the injection signal calculation module 330generates the warning-indication voltage signal with a ditheredfrequency, which is a time varying frequency around a predeterminedswitching frequency of the control loop of the motor 46. Alternatively,or in addition, in one or more examples, the injection signalcalculation module 330 generates the warning-indication voltage signalwith a fixed frequency of the control loop.

Further, in one or more examples, the injection signal calculationmodule 330 generates multiple warning injection signals for multiplecommands, for example, a combination of different signals, such assimultaneous torque and voltage injection signals. The differentinjection signals may be constant value signals or periodically varyingsignals generated using fixed or varying (order based) frequencies. Inone or more examples, the combination of the injection signals are fedin a coordinated manner into the control loop to generate the driverwarning feedback.

Further yet, in one or more examples, the injection signal calculationmodule 330 generates injection signals that simulate sensor errors,which cause the system behavior modification. For example, the sensorerror injection signals include gain or offset errors in current,position, voltage, and/or temperature signals, or any other sensorsignals used in the EPS 40, such as those that are used by the steeringcontrol 210, motor control 230, or any other component of the controller16. In the case of a resolver type position sensor (sine-cosine sensor),a quadrature error between the sine and cosine signal could also besimulated. The injection signal calculation module 330, in other words,manipulates one or more sensor signals received by the controller 16 (orany other component) by calculation of a constant value or a pulsatingsignal to be injected in the sensor signal(s) to create a sensor errorcondition. In one or more examples, the error signal injection isperformed as harmonic injection in the sensor signals.

The sensor signals may be modified in this manner, by injecting anerroneous pulsation in the sensor signals, in the case where the motorcontrol loop rejects the warning injection signals for the current,torque, and/or voltage commands, as disturbances. For instance, voltagesignals are disturbance signals for the motor control current loop, andwhen a high bandwidth feedback current control loop is employed, thesesignals may be rejected (in part) by the control loop. This isparticularly the case for voltage signals at lower frequencies.

In one or more examples, the injected signals simulate error conditionsin one or more hardware components (such as inverter or gate drives). Inresponse to the simulated errors being introduced, and further beingdetected by the fault monitoring system 240, a driver warning feedbackis generated. For instance, an error condition simulation may includesetting one of the voltage outputs of the voltage command generationmodule to zero or to simulate a lower FET short of one of the phase legsof the inverter, and the like. Other error simulations are possible inother examples.

The warning signal(s) injected into the base commands causes the driverwarning feedback to be tactile, acoustic, or a combination of both. Thefrequency of the pulsation used for the warning signal injectiondetermines whether the warning feedback is tactile, acoustic or acombination. For example, the torque or current commands are used forgenerating tactile feedback because of the low bandwidth control loopimplementation and control loop bandwidth limitations, for the torqueand current commands. Alternatively, or in addition, voltage injectionis used for acoustic feedback because relatively higher frequencies maybe injected directly in the voltage commands, compared to torque andcurrent commands. Further, the injection mechanisms, such as signaltransmission paths in the EPS 40, may also partly lead to the use of onetype of signal injection for generating the tactile and/or acousticwarning feedback.

Referring back to the FIG. 3, the fault duration module 320 determinesthe duration for which the fault is ongoing. For example, the faultduration module 320 keeps track, using a non-volatile memorysave/restore feature, if the fault is ongoing across multiple ignitioncycle, number of miles the fault has been ongoing, amount of time theEPS 40 has been operated with the ongoing fault, and other suchattributes associated with the ongoing fault. The fault duration module320 may further track a number of times a driver feedback has beenprovided regarding the ongoing fault. Accordingly, based on the trackedinformation, the fault duration module 320 modifies the injection signalamplitudes. Alternatively, or in addition, the fault duration module 320modifies the injection signal to provide the injection signals inbursts, i.e., an intermittent injection.

FIG. 4 illustrates a flowchart of an example method of providing adriver warning feedback according to one or more embodiments. The methodincludes detecting a fault condition with the EPS 40, as shown at block405. The fault monitoring system 240 detects the fault condition, whichmay be a diagnostic or a prognostic condition. The fault monitoringsystem 240 accordingly sets a diagnostic and/or a prognostic flag. Thedriver warning system 250 monitors the fault condition flags andgenerates a driver warning feedback in response.

Generating the driver warning feedback includes the FMA module 310determining a type of warning feedback to generate, as shown at block410. For example, the FMA module 310 may determine the type of warningfeedback to be a tactile feedback, an acoustic feedback, or acombination thereof. The type of warning feedback may be determinedbased on the type of flag that is set. Alternatively, or in addition,the type may be determined based on the type of fault condition.

Based on the driver warning feedback to be generated the injectioncalculation module 330 computes a warning injection signal, as shown atblock 420. In one or more examples, the warning injection signal is aperiodic signal. Computing the warning injection signal includesdetermining an amplitude, and frequency of the signal. For example, awarning injection signal for generating an acoustic driver warningfeedback is different from warning injection signal for generating atorque driver warning feedback. In one or more examples, the injectionsignal calculation module 320 computes the amplitude, phase, andfrequency based on one or more control signals of the EPS 40, such asmotor velocity, handwheel velocity, motor position, vehicle speed, orany other control signal. In one or more examples, the warning injectionsignal may not be a periodic frequency, rather a constant signal withzero frequency.

Further yet, the method includes determining whether a duration of thefault condition exceeds a predetermined threshold, as shown at block430. The predetermined threshold may be a configurable value, which maybe computed at real time in one or more examples, for example based onadditional fault conditions/changes in the EPS 40. If the predeterminedthreshold is not exceeded, the calculated warning injection signal isnot modified, and the warning injection signal is sent to the motorcontrol loop to generate tactile/acoustic driver warning feedback, asshown at block 450.

If the duration is exceeded, the fault duration monitoring module 320adjusts the warning injection signal, as shown at block 440. Forexample, if the fault condition has existed over multiple ignitioncycles, the intensity of the driver warning feedback is adjustedaccordingly, for example, increased. The intensity is adjusted byadjusting the amplitude, phase, and/or frequency of the warninginjection signal. For example, depending on a severity of the faultcondition, which may be predetermined and accessible via a look uptable, the frequency at which the driver warning feedback is provided isvaried. Alternatively, or in addition, based on the severity, theamplitude is varied. Alternatively, or in addition, based on theseverity, a phase is varied. In one or more examples, all threeparameters, the amplitude, the frequency, and the phase, or acombination thereof is varied.

The modified warning injection signal is then delivered into the motorcontrol loop to generate tactile/acoustic driver warning feedback, asshown at block 450. The delivery location of the warning injectionsignal is based on the type of command being modified. For example, if atorque command is being modified, the warning injection signal isinjected to a blend module, such as an adder, that receives the torquecommand and superimposes the warning injection signal onto the basetorque command. The modified torque command is then provided to themotor control system for generating a modified torque using the motor46. Alternatively, or in addition, if the current command is beingmodified, the warning injection signal is superimposed by a blend moduleonto the current command, and the modified current command is then usedfor generating the torque. Alternatively, or in addition, the voltagecommand is modified by superimposing the warning injection signal andthe thus modified voltage command is used by the motor control system togenerate a corresponding torque from the motor 46. Further, instead ofsuperimposing or blending, the original control signals includingtorque, current and voltage may be replaced altogether by the warningsignal values.

The torque generation by the motor provides a tactile and/or acousticfeedback to the driver because the modified commands change the assisttorque provided and/or the sound generated by the motor 46.

The technical solutions described herein thus facilitate alerting thedriver using the motor control loop in an EPS system under faultconditions, as determined through the diagnostic and prognosticsmonitoring. The technical solutions described herein facilitate usingcontrol signals that one or more components of the EPS are using createassist torque to create the driver warning feedback. The technicalsolutions described herein facilitates generating acoustic and tactiledriver feedback warning. Further, the technical solutions facilitatevarying the type and amount of feedback over time. The technicalsolutions described herein thus improve typical driver feedback systemsthat use passive feedback to the user by instead facilitating providingan active feedback to the driver using the electric actuator of the EPS.

FIG. 5 is an exemplary embodiment of a steer by wire steering (SbW)system according to one or more embodiments. It will be appreciated thatthe SbW system 40 shown and described can be used in an autonomous orsemi-autonomous vehicle or in a more conventional vehicle.

The SbW system 40 includes a handwheel actuator (HWA) 510 and aroadwheel actuator (RWA) 520.

The HWA 510 includes one or more mechanical components 512, such as thehandwheel 26 (steering wheel), steering column, a motor/inverterattached to the steering column either through a gear mechanism or adirect drive system. The HWA 510 further includes a microcontroller 514that controls the operation of the mechanical components 512. Themicrocontroller 514 receives and/or generates torque via the one or moremechanical components 512.

The RWA includes one or more mechanical components 522, such as asteering rack and/or pinion coupled to a motor/inverter through aball-nut/ball-screw (gear) arrangement, and the rack is connected to thevehicle roadwheels 44/tires through tie-rods. The RWA 520 also includesa microcontroller 524 that controls the operation of the mechanicalcomponents 522. The microcontroller 524 receives and/or generates torquevia the one or more mechanical components 522.

The microcontrollers 512 and 524 are coupled through electricalconnections that allow signals to be transmitted/received. As referredto herein, a controller can include a combination of the HWA controller512 and the RWA controller 522, or any one of the specificmicrocontrollers.

In one or more examples, the controllers 512 and 522 communicate witheach other through CAN interface (or other similar digital communicationprotocols). Guidance of the vehicle 5100 that is fitted with the SbWsystem 40 is performed by use of the mechanical components 522 of theRWA 520. The RWA 520 receives an electronic communication signal ofrotation of the steering wheel 26 by the driver. A driver controls thesteering wheel 26 to directionally control the vehicle 5100. The anglefrom HWA 510 is sent to the RWA 520 which performs position control tocontrol rack travel to guide the roadwheel 44. However, due to the lackof mechanical connection between the steering wheel 26 and the roadwheels 44, the driver is not provided with a feel for the road withouttorque feedback (unlike the case in an EPS as described earlier).

In one or more examples, the HWA 510 that is coupled to the steeringcolumn and steering wheel 26 simulates the driver's feel of the road.The HWA 510 may apply tactile feedback in the form of torque to thesteering wheel 26. The HWA 510 receives a rack force signal from the RWA520 to generate an appropriate torque feel for the driver.Alternatively, the handwheel angle and vehicle speed can also be used togenerate desired torque feel to the driver.

The technical solutions described herein facilitate using of theelectric drive portion of the SbW system 40, and more specifically, themotor control loop, to provide warning to the driver when a failure iseither about to occur (prognostics) or has already occurred (diagnostic)and the system 40 is still in operation. The warning may be providedthrough feedback to the driver in different ways, including tactilefeedback, acoustic feedback or a combination of both. Further, sincefail-safe conditions may potentially last over long periods of time (forinstance, if the driver decided to keep operating even with reducedassist for long durations), which may be within one ignition cycle orover multiple cycles, a time-varying warning mechanism is alsodescribed, where the amount of warning feedback is varied over time.

Safety requirements in contemporary SbW systems require advanced failuremonitoring, including both prognostics and diagnostics, for ensuringsafe operation of both the hardware and software. With improveddiagnostics, there is an increasing need for providing warning when thesystem is approaching a failure condition, or once the failure hasoccurred. Typical ways of alerting the driver that are used in SbWsystems as carryover technology from Electric Power Steering (EPS)systems, such as increasing the driver torque feedback using theHandwheel Actuator (HWA) so that the system feels heavy and the driveris, to an extent, cautioned to take the steering system for repair.

The technical solutions herein further improve the driver feedbackproviding by using the HWA 510 to provide both tactile and acousticfeedback to the driver. However, with the presence of two actuators inthe SbW system 40, i.e., the HWA 510 as well as the RWA 520, thetechnical solutions described herein facilitate additional schemes thatmay be implemented to provide driver warning when failures are eitherabout to occur (prognostics) or have already occurred (diagnostic) andthe SbW system 40 is still in operation, with increased flexibility.

According to one or more embodiments, the technical solutions describedherein facilitate the use of the HWA 510, more specifically the motorcontrol system within the HWA 510 to provide acoustic feedback, tactilefeedback or both through its direct connection to the driver. Thetechnical solutions described herein further facilitate using the RWA520 to provide acoustic feedback using the electric motor drive, as wellas tactile feedback to the driver through vibration of the vehiclechassis. Further, because fail-safe conditions may potentially last overlong periods of time (for instance, when the driver decided to keepoperating even with reduced assist for long durations), which may bewithin one ignition cycle or over multiple cycles, a time-varyingwarning mechanism is also described, where the amount of warningfeedback is varied over time. It should be noted that a warning system,according to one or more embodiments of the technical solutionsdescribed herein, may be implemented in an identical manner irrespectiveof the configuration of the motor control system (i.e., feedback orfeedforward control).

FIG. 6 depicts a block diagram and operational flow in a SbW system 40that includes the driver warning system 250 according to one or moreembodiments. The HWA 510 includes an inverter 613 that applies a voltage(V_(Hm)) to a motor 614 to generate the corresponding handwheel actuatormotor torque (T_(He)), which is the motor electromagnetic torque of thehandwheel actuator motor 614. The handwheel actuator motor torque isapplied to the mechanical system/components 615 of the SbW system 40,such as the handwheel 26, one or more gears and the like, to positionthe handwheel 26 at a position (⊖_(H)). In FIG. 6, (T*_(H)) is thehandwheel torque that is received from the driver as an input, while theremaining values with suffix ‘H’ represent handwheel actuator/motortorque values.

The inverter 613 applies the voltage based on a voltage command (V_(Hb))from a motor control system 612. The motor control system 612 generatesthe input voltage command based on an input torque command (T_(Hb)) thatis generated by a handwheel actuator motor torque command generator 611.The handwheel actuator motor torque command generator 611 generates theinput torque command based on a reference torque that is provided by areference torque generator 610, which in turn is based on a rack force,among other parameters, that is measured at the RWA 520 by a rack forceobserver 630.

In one or more examples, the input voltage command (V_(Hb)) is modifiedby the driver warning system 250 by injecting a first injection signal(V_(Hw)) to generate a modified input voltage command (V*_(Hm)) that isreceived by the inverter 613. The modification may include blending theinput voltage command and the first injection signal using an adder, orany other blending technique. The first injection signal in this case isa voltage injection signal.

Alternatively, or in addition, the input torque command (T_(Hb)) ismodified by the driver warning system 250 by injecting the firstinjection signal (T_(Hw)) to generate a modified input torque command(T*_(Hm)) that is received by the motor control system 612. Themodification may include blending the input torque command and the firstinjection signal using an adder, or any other blending technique. Thefirst injection signal in this case is a torque injection signal.

Further, based on the position (⊖_(H)) of the steering wheel 26, aposition command generator 620 generates an input position command(θ*_(H)) for a roadwheel position controller 621. The roadwheel positioncontroller 621 generates an input torque command (T*_(Rb)) to provide toa motor control system 622 of the RWA 520. The motor control system 622,in turn, generates a corresponding input voltage command (V*_(Rb)) thatan inverter 623 converts into an input voltage (V_(Rm)) for a motor 624of the RWA 520. The motor 624 generates a torque (T_(Re)) that isapplied to the one or more mechanical system/components 625 of thevehicle 650 of which the SbW system 40 is a part. The components 625include the roadwheel 44, which may be correspondingly positioned(⊖_(R)). The position/displacement of the components 625 is monitored bythe rack force observer 630 to generate the reference torque ({tildeover (T)}_(R)) that is used by the HWA 510 to generate the handwheeltorque and position as described herein.

In one or more examples, the input voltage command (V*_(Rb)) is modifiedby the driver warning system 250 by injecting a second injection signal(V_(Rw)) to generate a modified input voltage (V*_(Rm)) that is receivedby the inverter 623. The modification may include blending the inputvoltage command and the second injection signal using an adder, or anyother blending technique. The second injection signal in this case is avoltage injection signal.

Alternatively, or in addition, the input torque command (T*_(Rb)) ismodified by the driver warning system 250 by injecting the secondinjection signal (T_(Rw)) to generate a modified input torque command(T*_(Rm)) that is received by the motor control system 622. Themodification may include blending the input torque command and thesecond injection signal using an adder, or any other blending technique.The second injection signal in this case is a torque injection signal.

The driver warning system 250 generates the injection signal(s) based onthe output of the fault monitoring system 240. As described herein, thefault monitoring system 240 generates a diagnostic flag (D) and aprognostic flag (P). (See FIG. 3).

It should be noted that in both, the HWA 510 and the RWA 520, theinjection signal from the driver warning system 250 may be a currentinjection signal that is used to modify a current command that therespective motor control systems 612/622 generate for operating therespective motors 614/624.

The injection signals generated by the driver warning system 250 providedriver warning by modifying the input commands to the electric drive(motor control) systems 612/622 of the HWA 510 and the RWA 520. Theinjected signals are superimposed on the base signals as calculated bythe various functions. As mentioned earlier, the driver warning feedbackmay be tactile, acoustic or a combination of both.

In general, the torque, current and voltage pulsating command signalinjections may be performed by the driver warning system 250. The torquecommand injection may be of fixed or varying (order based) frequency,and may be a function of other signals, including velocity,acceleration, bridge voltage etc. Further, direct pulsating componentinjection in current commands may be performed instead of torque tocurrent command conversion. Voltage command injection may be of fixed orvarying (order based) frequency. Additionally, voltage signals withdithered frequency (time varying frequency around a nominal switchingfrequency) of control loop may be injected. Alternatively, a low fixedfrequency of control loop may also be used to produce tonal noise. Inone or more examples, a combination of torque, current, and voltagecommands may be injected in a coordinated manner to produce simultaneousacoustic and tactile feedback.

Alternatively, or in addition, for providing driver warning, a sensorerror injection is performed that includes injection of gain, offset orharmonic errors in the current, position, voltage or temperaturesensors. For example, sensor error injection is used in cases wherecommand injections may be rejected by the control loops (in the HWA510/RWA 520) as disturbances.

In one or more examples, the injection signals include torque or currentcommands for tactile feedback owing to their low bandwidth control loopimplementation (control loop bandwidth limitations) and limitedmechanical plant responsiveness. Further, voltage injection commands areused for providing acoustic feedback because higher frequencies can beinjected directly in the voltage command (compared to current/torquecommands).

Note that while the injection signals or commands are specified to betorque, current or voltage, the actual physical signals that cause thetactile and acoustic signature (or variation) are the torsional torqueon the shaft of the rotor and the radial force applied on the stator,both generated by the electromagnetic fields within the electric motor.For instance, when a very high frequency voltage is injected, it resultsin a varying radial force on the stator, causing the stator to vibrate,and thus causes a pressure variation in the air around it, whichultimately then results in an acoustic noise that may propagate throughdifferent transmission paths in the SbW system as well as the vehicle.This radial vibration may also result in a tactile feedback due to thephysical motion (in the radial direction) of the stator. Finally, thetorsional torque on the rotor shaft primarily generates tactilefeedback, it may also sometimes result in acoustic noise, depending thefrequency of the variation.

The technical solutions described herein accordingly facilitate usingthe RWA 520 to provide warning to the driver even though the RWA 520 isnot directly connected to the driver, for example, by vibration of thevehicle 650 directly (because the RWA 520 is directly connected to thevehicle 650).

As shown in FIG. 6, the first and second injection signals for the HWA510 and the RWA 520, respectively, are generated based on a common faultmonitoring system 240 that provides the D and P flags to the driverwarning system 250. Alternatively, the SbW system 40 uses separate faultmonitoring systems for the HWA 510 and the RWA 520.

FIG. 7 depicts a block diagram with separate fault monitoring systemsfor the HWA 510 and the RWA 520 according to one or more embodiments. AHWA fault monitoring system 710 monitors the operation of the HWA 510and detects an occurrence of a fault in the operation. The HWA faultmonitoring system 710 generates a corresponding set of output flagsD_(H) and P_(H). The driver warning system 250 includes a correspondingHWA driver warning system 715 that receives the flags D_(H) and P_(H) todetermine the driver feedback to be generated based on the flag values.

A separate RWA fault monitoring system 720 monitors, substantiallyconcurrently with the HWA fault monitoring system 710, the operation ofthe RWA 520 and detects an occurrence of a fault in the operation. TheRWA fault monitoring system 720 generates a corresponding set of outputflags D_(R) and P_(R). The driver warning system 250 includes acorresponding RWA driver warning system 725 that receives the flagsD_(R) and P_(R) to determine the driver feedback to be generated basedon the flag values.

The driver warning system 250 further includes a driver warningcoordination module (DWCM) 750 that receives as input, the outputgenerated by the HWA driver warning system 715 and the RWA driverwarning system 725. The DWCM 750 generates one or more injection signalsbased on the inputs. For example, the DWCM 750 determines whether togenerate driver feedback only via the HWA 510, only via the RWA 520, orusing a combination of the two. Further, the DWCM 750 determines whatinjection signals to generate for each of the HWA 510 and the RWA 520.For example, as described earlier, the injection signals can be one or acombination of voltage signals, current signals, and torque signals.

In one or more examples, tactile warning feedback may be generated bythe HWA 510 only, and the acoustic warning is partly generated by boththe HWA 510 and the RWA 520 together. Such warning generation sharing isperformed in a coordinated manner by the DWCM 750. The DWCM 750arbitrates and determines how the two actuators share and apply thewarning signals (for instance, by monitoring the operating conditions ofboth modules). It should be noted that the DWCM 750 may reside in eitherthe HWA 510 or the RWA 520 subsystems, or may be a separate system.

FIG. 8 depicts a flowchart of a method for generating a driverfeedback/warning in a SbW system according to one or more embodiments.The method includes detecting a fault in the HWA 510 by the handwheelfailure monitoring system 710, at 805. The method further includesdetecting a fault in the RWA 520 by the handwheel failure monitoringsystem 710, at 807. The HWA fault detection and the RWA fault detectioncan occur concurrently, in one or more examples. The fault detection isperformed as described herein (see FIG. 4 for example). In one or moreexamples, the fault detection results in one or more fault indicationflags being set such as diagnostic flag(s) and prognostic flag(s).

The method further includes determining type(s) of driver feedback togenerate in response to the detected fault(s) in the HWA 510 and/or theRWA 520, at 810. For example, the type of feedback can include one ormore of a tactile feedback, an acoustic feedback, and the like. The typeof feedback to be provided can be determined using one or moretechniques described herein.

If a feedback via the HWA 510 is to be provided, the method includesgenerating a first injection signal, at 820 and 822. For example, thedriver warning system 250 generates the first injection signal to modifyamplitude, frequency, or any other attribute of an input command for amotor loop within the HWA 510, as described herein. The first injectionsignal can be a torque signal, a current signal, or a voltage signal, ora combination thereof. Depending on the type of the first injectionsignal, the first injection signal is delivered to the motor loop of theHWA 510 to modify the corresponding input command, at 824. Modifying theinput command(s) causes the motor 614 of the HWA 510 to generate atactile/acoustic feedback for the driver.

Further, if a feedback via the RWA 520 is to be provided, the methodincludes generating a second injection signal, at 830 and 832. Forexample, the driver warning system 250 generates the second injectionsignal to modify amplitude, frequency, or any other attribute of aninput command for a motor loop within the RWA 520, as described herein.The second injection signal can be a torque signal, a current signal, ora voltage signal, or a combination thereof. Depending on the type of thesecond injection signal, the second injection signal is delivered to themotor loop of the RWA 520 to modify the corresponding input command, at834. Modifying the input command(s) causes the motor 624 of the RWA 520to generate a tactile/acoustic feedback for the driver.

In one or more examples, delivering the first injection signal and thesecond injection signal includes coordinating the two injection signalsgenerated by the handwheel actuator driver warning system 715 and theroadwheel actuator driver warning system 725 respectively to determinethe driver feedback, at 850. For example, the coordination may includearbitrating between the injection signals if they are of the same typeand selecting the greater value among the two. For example, considerthat the handwheel actuator driver warning system 715 generates a firstwarning injection signal and the roadwheel actuator driver warningsystem 725 generates a second warning injection signal, both includingvoltage modification command. Say, the two modification command hasvalues V₁ and V₂, respectively, and are both to be injected into the HWA510 (or the RWA 520). In one or more examples, the coordination mayinclude selecting the injection signal with the larger value among V₁and V₂ to be injected into the HWA 510 (or the RWA 520). Thecoordination may include selecting the injection signal in any othermanner, for example, selecting the smaller value, computing a mean, aweighted average of the two signals, or any other technique or acombination thereof.

The technical solutions described herein accordingly facilitate multiplemechanisms for alerting the driver using the motor control loop in theHWA and RWA subsystems of a SbW system under fault conditions determinedthrough the diagnostic and prognostics monitoring module.

According to one or more embodiments, a steering system includes a firstmotor control system that sends a first command to a first motor in ahandwheel actuator. The steering system further includes a second motorcontrol system that sends a second command to a second motor in aroadwheel actuator. The steering system further includes a faultmonitoring system that sets a fault indication flag by monitoring one ormore components of the steering system. The steering system furtherincludes a driver warning system that generates a warning injectionsignal in response to the fault indication flag being set. The handwheelactuator generates a first driver feedback by modifying the firstcommand using the warning injection signal, and sending the modifiedfirst command to the first motor. Further, the roadwheel actuatorgenerates a second driver feedback by modifying the second command usingthe warning injection signal, and sending the modified second command tothe second motor.

In one or more examples, the second command that is modified is avoltage command. In one or more examples, the first command that ismodified is a torque command. The steering system where the secondcommand that is modified is a current command. The steering system wherethe second command that is modified is a result of a sensor signalsimulation by the fault monitoring system.

In one or more examples, the warning injection signal includes a firstinjection signal and a second injection signal, and the driver warningsystem includes a handwheel driver warning system that generates thefirst injection signal based on a fault detected in the handwheelactuator, and a roadwheel driver warning system that generates thesecond injection signal based on a fault detected in the roadwheelactuator. In one or more examples, the driver warning system furtherincludes: a driver warning coordination module that arbitrates the firstinjection signal and the second injection signal to generate the warninginjection signal.

In one or more examples, each of the handwheel driver warning system andthe roadwheel driver warning system includes a fault duration modulethat monitors a duration of the fault indication being set, where thewarning injection signal is determined based on the duration. In one ormore examples, each of the handwheel driver warning system and theroadwheel driver warning system includes a fault monitoring andarbitration module that determines a type of the driver feedback basedon the fault indication flag. In one or more examples, each of thehandwheel driver warning system and the roadwheel driver warning systemincludes an injection signal calculation module that computes thewarning injection signal based on the type of the driver feedback to beprovided, the computation includes determining a frequency, phase, andamplitude of the warning injection signal.

In one or more examples, the fault monitoring system includes ahandwheel driver warning system that detects a fault in the operation ofthe handwheel actuator; and a roadwheel fault monitoring system thatdetects a fault in the operation of the handwheel actuator. The warninginjection signal includes a plurality of injection signals, a firstinjection signal for the first command for the handwheel actuator, and asecond injection signal for the second command for the roadwheelactuator.

According to one or more embodiments, a method for providing driverwarning feedback using a steer by wire system includes receiving anindication flag that is indicative of a fault in one or more componentsof the steering system. The method further includes generating a warninginjection signal based on the fault indication flag being set. Themethod further includes generating, by a handwheel actuator, a firstdriver feedback by modifying a first input command with the warninginjection signal, and sending the modified first input command to afirst motor of the handwheel actuator. The method further includesgenerating, by a roadwheel actuator, a second driver feedback bymodifying a second input command with the warning injection signal, andsending the modified second input command to a second motor of theroadwheel actuator.

According to one or more embodiments a driver warning feedback systemincludes a handwheel fault monitoring system configured to monitor afirst fault indication flag that is indicative of a fault in operationof one or more components of a handwheel actuator. The driver warningfeedback system further includes a handwheel actuator driver warningsystem configured to generate a first driver feedback via the handwheelactuator based on the first fault indication flag being set. The driverwarning feedback system further includes a roadwheel fault monitoringsystem configured to monitor a second fault indication flag that isindicative of a fault in operation of one or more components of aroadwheel actuator. The driver warning feedback system further includesa roadwheel actuator driver warning system configured to generate asecond driver feedback via the roadwheel actuator based on the secondfault indication flag being set. The driver warning feedback systemfurther includes driver warning coordination module configured tocompute a warning injection signal based on the first driver feedbackand the second driver feedback, and send the warning injection signal tomodify a command sent to a motor to generate a driver warning.

It should be noted that although the technical solutions herein aredescribed to generate a feedback for a driver using a warning system inthe context of a vehicle, such as by using a steering system, thetechnical solutions herein can be used as a warning system thatgenerates an audible sound using one or more motors. The warning systemincludes the actuators and fault monitoring system as described herein,the actuators including respective set of components and motors that areused to generate an audible sound/noise as a warning notification. Thewarning system accordingly generates audible noise without using aspeaker or other such typical device for generating an acousticwarning/feedback.

The present technical solutions may be a system, a method, and/or acomputer program product at any possible technical detail level ofintegration. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent technical solutions.

Aspects of the present technical solutions are described herein withreference to flowchart illustrations and/or block diagrams of methods,apparatus (systems), and computer program products according toembodiments of the technical solutions. It will be understood that eachblock of the flowchart illustrations and/or block diagrams, andcombinations of blocks in the flowchart illustrations and/or blockdiagrams, can be implemented by computer readable program instructions.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present technical solutions. In this regard, eachblock in the flowchart or block diagrams may represent a module,segment, or portion of instructions, which comprises one or moreexecutable instructions for implementing the specified logicalfunction(s). In some alternative implementations, the functions noted inthe blocks may occur out of the order noted in the Figures. For example,two blocks shown in succession, in fact, may be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts or carry outcombinations of special purpose hardware and computer instructions.

It will also be appreciated that any module, unit, component, server,computer, terminal or device exemplified herein that executesinstructions may include or otherwise have access to computer readablemedia such as storage media, computer storage media, or data storagedevices (removable and/or non-removable) such as, for example, magneticdisks, optical disks, or tape. Computer storage media may includevolatile and non-volatile, removable and non-removable media implementedin any method or technology for storage of information, such as computerreadable instructions, data structures, program modules, or other data.Such computer storage media may be part of the device or accessible orconnectable thereto. Any application or module herein described may beimplemented using computer readable/executable instructions that may bestored or otherwise held by such computer readable media.

While the technical solutions are described in detail in connection withonly a limited number of embodiments, it should be readily understoodthat the technical solutions are not limited to such disclosedembodiments. Rather, the technical solutions can be modified toincorporate any number of variations, alterations, substitutions, orequivalent arrangements not heretofore described, but which arecommensurate with the spirit and scope of the technical solutions.Additionally, while various embodiments of the technical solutions havebeen described, it is to be understood that aspects of the technicalsolutions may include only some of the described embodiments.Accordingly, the technical solutions are not to be seen as limited bythe foregoing description.

What is claimed is:
 1. A steering system comprising: a first motorcontrol system that sends a first command to a first motor in ahandwheel actuator; a second motor control system that sends a secondcommand to a second motor in a roadwheel actuator; a controllerconfigured that; sets a fault indication flag by monitoring one or morecomponents of the steering system; and generates a warning injectionsignal in response to the fault indication flag being set; the handwheelactuator configured to generate a first driver feedback by modifying thefirst command using the warning injection signal, and sending themodified first command to the first motor; and the roadwheel actuatorconfigured to generate a second driver feedback by modifying the secondcommand using the warning injection signal, and sending the modifiedsecond command to the second motor, wherein the warning injection signalcomprises a first injection signal and a second injection signal, andthe controller; generates the first injection signal based on a faultdetected in the handwheel actuator; generates the second injectionsignal based on a fault detected in the roadwheel actuator; andarbitrates the first injection signal and the second injection signal togenerate the warning injection signal.
 2. The steering system of claim1, wherein the second command that is modified is a voltage command. 3.The steering system of claim 2, wherein the first command that ismodified is a torque command.
 4. The steering system of claim 2, whereinthe first command that is modified is a current command.
 5. The steeringsystem of claim 1, wherein the second command that is modified inresponse to a sensor signal simulation by the controller.
 6. Thesteering system of claim 1, wherein that the controller monitors aduration of the fault indication being set, wherein the warninginjection signal is determined based on the duration.
 7. The steeringsystem of claim 6, wherein that the controller determines a type of thedriver feedback based on the fault indication flag, wherein the type ofdriver feedback includes at least one of a tactile feedback and anacoustic feedback.
 8. The steering system of claim 7, wherein that thecontroller computes the warning injection signal based on the type ofthe driver feedback to be provided, the computation includes determiningat least a frequency and an amplitude of the warning injection signal.9. The steering system of claim 1, wherein the controller detects afault in the operation of the handwheel actuator; and detects a fault inthe operation of the roadwheel actuator.
 10. A method for providingdriver warning feedback using a steer by wire system, the methodcomprising: receiving an indication flag that is indicative of a faultin one or more components of the steering system; generating a warninginjection signal based on the fault indication flag being set;generating, by a handwheel actuator, a first driver feedback bymodifying a first input command with the warning injection signal, andsending the modified first input command to a first motor of thehandwheel actuator; generating, by a roadwheel actuator, a second driverfeedback by modifying a second input command with the warning injectionsignal, and sending the modified second input command to a second motorof the roadwheel actuator, wherein the warning injection signalcomprises at least one of a first injection signal and a secondinjection signal, and wherein; the first injection sinal is generated inresponse to a fault being detected in the handwheel actuator, and thesecond injection signal is generated in response to a fault beingdetected in the roadwheel actuator; and arbitrating, in response togenerating the first injection signal and the second injection signalthe first injection signal and the second injection signal to generatethe waming injection signal.
 11. The method of claim 10, wherein thewarning injection signal is determined based on a duration for which thefault indication flag is set.
 12. The method of claim 10, wherein firstdriver feedback is at least one of a tactile feedback and an acousticfeedback, and the second driver feedback is at least one of a tactilefeedback and an acoustic feedback.
 13. A driver warning feedback systemcomprising: a controller configured to; monitor a first fault indicationflag that is indicative of a fault in operation of one or morecomponents of a handwheel actuator; generate a first driver feedback viathe handwheel actuator based on the first fault indication flag beingset; and compute a warning injection signal based on the first driverfeedback and the second driver feedback, and send the warning injectionsignal to modify a command sent to a motor to generate a driver warning,wherein the warning injection signal comprises a first injection signaland a second injection signal, and wherein the controller is furtherconfigured to arbitrate between the first injection signal and thesecond injection signal to generate the warning injection signal. 14.The driver warning feedback system of claim 13, wherein the warninginjection signal is superimposed on at least one of a torque command, acurrent command, a voltage command, and a sensor signal.
 15. The driverwarning feedback system of claim 13, wherein the driver warning that isgenerated includes at least one of a tactile feedback and an acousticfeedback.
 16. A warning system comprising: a first motor control systemthat sends a first command to a first motor in a first actuator; asecond motor control system that sends a second command to a secondmotor in a second actuator; a controller that; sets a fault indicationflag by monitoring one or more components of the first and second motorcontrol systems and generates a warning injection signal in response tothe fault indication flag being set, wherein the warning injectionsignal comprises a first injection signal and a second injection signal,the first injection signal is generated based on a fault detected in thefirst actuator; the second injection signal is generated based on afault detected in the second actuator; and the controller arbitrates thefirst injection signal and the second injection signal to generate thewarning injection signal; the first actuator configured to generate afirst feedback using the first motor by modifying the first commandusing the warning injection signal, and sending the modified firstcommand to the first motor; and the second actuator configured togenerate a second feedback by modifying the second command using thewarning injection signal, and sending the modified second command to thesecond motor.